Bore holes in more or less homogeneous materials display a bore hole wall parallel to the bore hole axis, which is undesirable in numerous applications. This, for example, is especially true for anchor holes in synthetic stone, i.e., concrete, in which any anchoring device is to be secured. For this reason it is frequently desired in all possible types of borings to provide back cuts or relief in the bore hole wall to improve the fastening of anchoring devices in the bore hole such as anchor holes or to achieve widening for other purposes.
In similar devices disclosed in U.S. Pat. No. 4,153,121 (U.K. No. 1,554,730; DE-OS No. 2,657,849) and U.S. Pat. No. 4,186,810 (DE-OS No. 2,730,026), the carrier housing forms a cutting head, which can be installed in the bore hole in a predetermined position and rotated by means of a fluid pressure actuated drive. The cutting head radially encloses cutting tools which are extendable by means of fluid pressure actuated drives and intermittently movable from a rest position inside the crosssectional contour of the cutting head radially outward into an operating position, in which the cutting tool or member, formed as an impact cutting body, protrudes radially beyond the crosssectional contour of the cutting head and can work on the bore hole wall or partition in a reaming or undercutting manner.
For activation of the reaming or cutting tools, whose cutting member is formed as a single cutting body of tungsten carbide, a pressure actuated adjusting device is used, which may be operated from a location outside of the bore hole and which transmit radially oscillating, thrust or impact motions to the cutting tools.
These kinds of arrangements with radial linear motion of the cutting tools, require a relatively large diameter cutting head to house the radially directed pressure actuating piston. They are also attrition prone under the frequently harsh working conditions, because the radial guide surfaces which take and resist the tilting moments of force on the cutting tools are highly loaded, cause difficulties in the durable sealing of the pressure medium spaces and require considerable maintenance and repair effort, especially when it becomes necessary to replace used cutting members.
This invention provides an undercutting and/or reaming apparatus that can be manufactured and used within minimal constructional dimensions, has low production cost, is sturdy and provides easy tool changes and high reaming or cutting efficiency.
The invention solves the task or problem by providing various improvements in the distinguishing portions of an undercutting device and the significant arrangements thereof disclosed and claimed hereinbelow.